I’m running CentOS 64 bit, and jsut found out I am running prefork MPM on my dual quad xeon. I was told worker will give me lower memory usage, and higher performance, since I run a very high traffic website.

What is Varnish?

Varnish is an open source, high performance http accelerator that sits in front of a web stack and caches pages. This caching layer is very configurable and can be used for both static and dynamic content.

One great thing about Varnish is that it can improve the performance of your website without requiring any code changes. If you haven’t heard of Varnish (or have heard of it, but haven’t used it), please read on. Adding Varnish to your stack can be completely noninvasive, but if you tweak your stack to play along with some of varnish’s more advanced features, you’ll be able to increase performance by orders of magnitude.

Our Use Case

One of Factual’s first high profile projects was Newsweek’s “America’s Best High Schools: The List”. After realizing that we had only a few weeks to increase our throughput by tenfold, we looked into a few options. We decided to go with Varnish because it was noninvasive, extremely fast and battlefield tested by other companies. The result yielded a system that performed 15 times faster and a successful launch that hit the front page of msn.com. Varnish now plays a major role in our stack and we’re looking to implement more performance tweaks designed with Varnish in mind.

A Simple Use Case

The easiest and safest way to add Varnish to your stack is to serve and cache static content. Aside from using a CDN, Varnish is probably the next best thing that you can use for free. However, dynamic content is where you can squeeze real performance out of your stack if you know where and how to use it. This guide will only scratch the surface on how Varnish can drastically improve performance. Advanced features such as edge side includes and header manipulation allow you to leverage Varnish for even higher throughput. Hopefully, we’ll get to more of these advanced features in future blog posts, but for now, we’ll just give you an introduction.